Moment-cancelling 4-stroke engine

ABSTRACT

A moment-cancelling, four-stroke engine is disclosed. The engine includes a first cylinder having a first piston and a second cylinder having a second piston, a first crankshaft operably connected to the first piston and a second crankshaft operably connected to the second piston. The first crankshaft rotates in a first direction and the second crankshaft rotates in a second direction that is opposite the first direction to cancel the moments applied to the engine and reduce engine vibration.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference under 37 CFR 1.57.

This application claims the benefit of U.S. Provisional Application No.62/020,695, entitled “MOMENT-CANCELLING 4-STROKE ENGINE,” filed Jul. 3,2014, the entirety of which is incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates generally to four-stroke internal combustionengines.

DESCRIPTION OF THE RELATED ART

Despite a one hundred and twenty year history of the four strokeengines, significant advancements to engine design are desired forfuture motorcycles, automobiles, aircraft, and/or boats. Two fundamentalbut persistent problems with existing engines are optimum combustion andoperator-friendly operation.

Optimum combustion preferably includes consideration of powerproduction, emissions, detonation prevention, engine efficiency, bettergas mileage, engine life, engine cooling while avoiding the consequencesof additional equipment, such as turbochargers, which can result inassociated costs and complexity.

Operator-friendly operation preferably includes consideration ofvibration, vehicle handling, engine reliability, use of available fuels,mean piston speed, endurance, engine lubrication, crankshaft torque,system simplicity, and minimized weight.

Clearly, the industry has need for a new 4-stroke engine that canoptimize performance of a multiplicity of characteristicssimultaneously. This disclosure describes an innovative 4-stroke enginethat simultaneously provides reliability, efficiency, and low emissionsin a single design.

Further, it is clear to someone skilled in the art that this design canbe made applicable to a family of engines in 2-cylinder, 4-cylinder,6-cylinder and 8-cylinder configurations. Further, based on the intendeduse of the engine, variants of the invention are possible.

SUMMARY OF THE INVENTION

One aspect of at least one embodiment of the invention is therecognition that it would be desirable to have an engine with improvedair flow or breathing capability in a compact design that reducesvibration.

In some embodiments, including the illustrated embodiment, a four-strokeengine is disclosed. The four-stroke engine comprises a first cylinderhaving a first piston and a second cylinder having a second piston, afirst crankshaft operably connected to the first piston and a secondcrankshaft operably connected to the second piston, wherein the firstcrankshaft rotates in a first direction and the second crankshaftrotates in a second direction. In some embodiments, the first directionis an opposite direction from the second direction. In some embodiments,the engine is water-cooled. In some embodiments, the engine has fourvalves. In some embodiments, the first and second pistons travel in thesame plane. In some embodiments, the first and second pistons areconfigured with a flat head.

In some embodiments, a bore diameter of each of the first and secondcylinders is between about 1.5 to 7.0 inches. In some embodiments, anoversquare ratio of the engine is greater than 1.0. In some embodiments,an oversquare ratio of the engine is greater than 1.78. In someembodiments, an engine squish is greater than 24% and less than 35%.

In some embodiments, a compression ratio of the engine is at least 9.1to 1. In some embodiments, a compression ratio of the engine is at least13.5 to 1. In some embodiments, a mean piston speed of the engine isless than 4200 feet per minute. In some embodiments, a mean piston speedof the engine is at least 1800 feet per minute. In some embodiments, themean piston speed of the engine is less than 3000 feet per minute.

In some embodiments, the cylinders are displaced a nominal distanceforward and aft from an intersection between the cylinders and acrankshaft axis to allow a connecting rod of each cylinder to bestraighter on a firing stroke of each cylinder.

In some embodiments, the engine may further comprise a porting systemcomprising of at least one intake valve and at least one outlet valveper cylinder, each of the intake and exhaust valves having a valve seatangle, a valve undercut angle, and an intake port angle, wherein thevalve seat angle of the at least one intake valve is between about 40-52degrees, the valve undercut angle of the at least one intake valve isbetween about 30-42 degrees, the valve seat angle of the at least oneexhaust valve is between about 40-52 degrees, the valve undercut angleof the at least one exhaust valve is between about 30-48 degrees, andthe intake port angle is between about 45 and 65 degrees. In someembodiments, an intake valve area to a piston area is betweenapproximately 28% and 38% when a piston diameter is between 1.5 and 7inches and a piston stroke is between 1.5 and 3.5 inches.

In some embodiments, the engine may further comprise a third cylinderand a fourth cylinder, wherein the first and third cylinders areoperably connected to the first crankshaft and the second and fourthcylinders are operably connected to the second crankshaft. In someembodiments, the engine may further comprise a fifth cylinder and asixth cylinder, wherein the first, third, and fifth cylinders areoperably connected to the first crankshaft and the second, fourth, andsixth cylinders are operably connected to the second crankshaft. In someembodiments, the engine may further comprise a seventh cylinder and aneighth cylinder, wherein the first, third, fifth, and seventh cylindersare operably connected to the first crankshaft and the second, fourth,sixth, and eighth cylinders are operably connected to the secondcrankshaft.

In some embodiments, the engine is mounted perpendicular to alongitudinal axis of the vehicle and the engine further comprises dualoverhead cams. In some embodiments, a cross-section of a majority or allof a valve seating surface is flat or straight such that at least amajority or all of an overall shape of the valve seating surface iscone-shaped. In some embodiments, at least a majority or all of across-section of a valve undercut surface is flat or straight such thatat least a majority or all of an overall shape of the valve undercutsurface is cone-shaped.

In another embodiment, including the illustrated embodiment, afour-stroke engine is disclosed. The four-stroke engine comprises afirst cylinder having a first piston, a second cylinder having a secondpiston, and a porting system connected to each of the first and secondcylinders, the porting system comprising at least one intake port percylinder and at least one exhaust port per cylinder, the intake andexhaust ports having a non-symmetric variable shape along a length ofeach port. In some embodiments, an oversquare ratio of the engine isgreater than 1. In some embodiments, the engine further comprises afirst crankshaft operably connected to the first piston and a secondcrankshaft operably connected to the second piston, wherein the firstcrankshaft rotates in a first direction and the second crankshaftrotates in a second direction. In some embodiments, the first and secondpistons are flat head pistons. In some embodiments, the engine iswater-cooled. In some embodiments, an intake valve area to a cylinderbore area is between approximately 28% and 38%, that is the intake valvearea is between 28% and 38% of the cylinder bore area, when a pistondiameter is between 1.5 and 7 inches. In some embodiments, a port areato a valve area is between 42% and 65%. In some embodiments, an intakeport area to a valve area is approximately 53.4%. In some embodiments,an exhaust port area to a valve area is between about 72% to about 88%.In some embodiments, an intake angle of the intake port is approximately7.9 degrees in a first direction from vertical. In some embodiments, anexhaust angle of the exhaust port is approximately 8.4 degrees in asecond direction opposite to the first direction from vertical.

In another embodiment, including the illustrated embodiment, afour-stroke engine is disclosed. The four-stroke engine comprises atleast one pair of cylinders, a first crankshaft operably connected toone cylinder of the at least one pair of cylinders, a second crankshaftoperably connected to the other cylinder of the least one pair ofcylinders, the first crankshaft configured to rotate in a firstdirection, the second crankshaft configured to rotate in a seconddirection that is opposite the first direction, and a porting systemcomprising two intake valves and two exhaust valves per cylinder. Insome embodiments, an average piston speed is less than 4200 feet perminute. In some embodiments, a compression ratio of the engine isbetween 9.1 and 13.5. In some embodiments, an oversquare ratio of theengine is greater than 1.0. In some embodiments, an oversquare ratio ofthe engine is 1.78.

In some embodiments, the engine is configured to power a motorcycle. Insome embodiments, the engine is configured to power an automobile. Insome embodiments, the engine is configured to power a helicopter orother aircraft. In some embodiments, the engine is configured to power aboat.

In another embodiment, including the illustrated embodiment, an airintake system for a four-stroke combustion engine is disclosed. The airintake system comprises at least one intake valve per cylinder of theengine and a throttle valve at an entrance to the cylinder, the throttlevalve configured to control air flow to the cylinder by receivingsignals from an electronic engine management system, the electronicengine management system configured to transmit signals to the throttlevalve such that a first position of the throttle valve corresponds to ahigh mileage mode of operation of the engine and a second position ofthe throttle valve corresponds to a high power mode of operation of theengine.

In another embodiment, including the illustrated embodiment, an internalcombustion engine is disclosed. The internal combustion engine comprisesa first cylinder having a first piston and a second cylinder having asecond piston, a first crankshaft operably connected to the first pistonand a second crankshaft operably connected to the second piston, acylinder head comprising at least one intake port and at least oneexhaust port per cylinder, each of the intake ports and the exhaustports connected to the cylinders such that fluid can pass through theintake ports into the cylinders and fluid can pass from the cylindersthrough the exhaust ports, each of the intake ports further comprisingan intake valve configured to control the flow of fluid through theintake ports, each of the exhaust ports further comprising an exhaustvalve configured to control the flow of fluid through the exhaust ports,the intake ports and the exhaust ports having a non-symmetric variableshape along a length of each port such that a valve seat angle of eachof the intake valves is between about 40-52 degrees, a valve undercutangle of each of the intake valves is between about 30-42 degrees, avalve seat angle of each of the exhaust valves is between about 40-52degrees, a valve undercut angle of each of the exhaust valves is betweenabout 30-48 degrees, and an intake port angle of each of the intakevalves and exhaust valves is between about 45 and 65 degrees, whereinthe first crankshaft rotates in a first direction and the secondcrankshaft rotates in a second direction such that the second directionis an opposite direction from the first direction. In some embodiments,a bore of each of the first and second cylinders is greater than 3.0inches. In some embodiments, an oversquare ratio of the engine isgreater than 1.0. In some embodiments, each of the first and secondpistons are flat top pistons and a squish area of each piston is between24%-35% of an area of the piston.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A: Isometric View of Moment Canceling Engine

FIG. 1B: Isometric View of Moment Canceling Engine Indicating SeveralAxes of the Engine

FIG. 1C: View of Front Side of Moment Canceling Engine

FIG. 1D: View of Right Side of Moment Canceling Engine

FIG. 2: Cross-sectional View of Moment Canceling Engine through Centerof Pistons

FIG. 3: Cross-section View of Moment Canceling Engine through Right Side

FIG. 4: Cross-sectional View of the Moment Cancelling Engine through theLeft Side

FIG. 5A: Isometric View of Moment Canceling Engine Sump

FIG. 5B: Second Isometric View of Moment Canceling Engine Sump

FIG. 6: Cross-sectional View of Moment Canceling Engine Valve TrainLayout

FIG. 7: Detail Cross-sectional View of Intake Valve and Cylinder Head

FIG. 8: Otto Cycle Illustration

FIG. 9: Isometric View of Crankshaft for the Moment-Cancelling 4. StrokeEngine

FIG. 10: Inlet Flow versus Valve Lift for Several Configurations ofInlet Ports for MC4S Engine

FIG. 11A: STRAIGHT TAPER Intake Porting System

FIG. 11B: IMPROVED TAPER Porting System

FIG. 11C: OPTIMIZED TAPER Porting System

FIG. 11D: Partial View of the OPTIMIZED TAPER Porting System of FIG. 11C

FIG. 12: Brake Mean Effective Pressure at Various RPM and CompressionRatios

FIG. 13: Peak BMEP for MC4S Engine over a Range of Compression Ratios

FIG. 14: Effects on Flow Ratio (Intake/Exhaust) for Various Valve LiftPositions

FIG. 15: Effects on Peak Horsepower for Various Intake/Exhaust FlowRatios

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following detailed description is directed to certain specificembodiments of the invention. However, the invention may be embodied ina multitude of different ways as defined and covered by the claims.

In the following description, numerous aspects of the engine provideadvantages over prior engine designs. References to certain aspects asimportant or significant does not imply that each and every one of thereferenced aspects are required in all embodiments of the invention toprovide advantages over the prior art.

In the illustrated embodiment, the water-cooled Moment-Cancelling4-Stroke Engine (MC4S) has twin vertical cylinders with aluminum alloycrankcase, cylinder, and head casting. The twin cylinders' crankshaftsare preferably orientated to be transverse and, preferably,perpendicular to the longitudinal axis of the vehicle, such as amotorcycle. In the preferred embodiment, the cylinders are displaced anominal distance forward and aft from their normal intersection with thecrankshaft axis allowing the connecting rod to run straighter on thefiring stroke. In one embodiment, the sump is one piece cast aluminumalloy. The cylinder bore is preferably liner-less and has a Nikasil(Trade Name for electrodeposited lipophilic nickel matrix siliconcarbide) coating for wear resistance. In some embodiments, the head isattached to the crankcase and sump by seven through bolts. Head sealingis preferably accomplished with custom-designed gaskets of multi-layeredsteel, such as those provided by Cometic Gasket Company.

FIGS. 1A and B show an isometric view of the MC4S engine. Shown are thecrankcase, cylinders, head casting, sump 106, and head bolts.Additionally, crankshafts 102, 104 are connected to the pistons via thepiston rods 108, 110. A gearing system 150 connects the crankshafts 102,104 to the transmission of the vehicle. FIG. 1B illustrates theorientation of the engine 100 relative to the longitudinal axis 200 ofthe vehicle. The engine 100 is desirably oriented such that thecylinders and by extension, the piston rods 108, 110 connected to thepiston within the cylinders, are in line with the longitudinal axis 200.The cylinder bore axis 204, an axis defining the vertical dimension ofthe cylinder oriented in the direction of travel of the piston withinthe cylinder, is desirably orthogonal to the longitudinal axis 200 ofthe vehicle. Desirably, the crankshafts 102, 104 rotate in oppositedirections (one crankshaft 102 rotates counter-clockwise, the othercrankshaft 104 rotates clockwise), as indicated by arrows 206, 208. Thecounter-rotating crankshafts 102, 104 preferably improve the balance ofthe engine 100, as will be described in further detail below. FIGS. 1C-Dillustrate other views of the engine 100. FIG. 1C illustrates a frontview of the engine 100. FIG. 1D illustrates a right side view of theengine 100 to indicate the cross-sections shown in FIGS. 2-4.

FIG. 2 shows a cross-section though the center of the MC4S engine 100allowing a view of the pistons 120, 122; piston rods 108, 110; cylinders130, 132; crankshafts 102, 104; and crankshaft gears. FIG. 3 shows across-sectional view of the MC4S engine 100 through the right side ofthe engine showing the oil pump, timing chain, cam shaft 302, exhaust,and transmission. FIG. 4 shows a cross-sectional view of the MC4S engineof the left side of the engine showing the end of the crankshafts 102,104 and attached crankshaft gears and bearing 410. FIGS. 5A and B showan isometric view of the oil sump 106 for the MC4S engine 100.

Moment Cancelling 4-Stroke Engine Features

The MC4S engine assembly makes use of a large bore diameter (in someembodiments, ranging from 1.5-7.0 inches) flat top piston with arelatively short stroke of preferably 1.5-5.0 inches. The configurationof one preferred embodiment includes a 5.0 inch bore diameter with 2.8inch stroke. Specifically, the MC4S engine is preferably designed tohave a bore diameter greater than the stroke length, called“oversquare.” In one embodiment, the MC4S is “oversquare” with a ratioof 1.78. Someone skilled in the art would understand that in otherembodiments the MC4S could be built with a range of “over square” ratiosfrom 1.1-4.5.

The MC4S engine is preferably designed with a specific amount of“squish”, which is the inward movement of air towards the center as thepiston approaches Top-Dead-Center of its stroke. The objective of thisdesign feature is to bring the largest possible amount of the air intocontact with the fuel during combustion. In some embodiments, for theflat top piston configuration, the squish area can range from 24%-35% ofthe area of the piston. In a preferred embodiment, the squish area isapproximately 31.5% or between 28%-33% of the piston area. This range ofsquish area significantly helps prevent the issue of detonation in thecombustion chamber. This is another example of the delicateinter-relationship of multiple design features in an optimumconfiguration of the preferred embodiment, specifically the pistonstroke in combination with the supply of air to the engine.

In a preferred embodiment, the engine has a mean piston speed of lessthan 4200 feet per minute. Empirical observation from a number ofproprietary race engines has shown that engine reliability is generallygreatest with a mean piston speed of 1800-5200. Further empiricalobservation has shown that piston engines for aircraft, such ashelicopters, with a mean piston speed of 1800-1900 feet generally havehigh reliability and that engines with over 5200 feet per minute may beprone to prematurely-shortened operational life.

FIG. 6 shows the Valve Train layout of the MC4S engine 100. Shown incross-section are the dual camshafts 602, 604, intake valve 620, exhaustvalve 622, cam followers 606, 608, and intake porting 630. Each cylinderpreferably has a single spark plug. The cam shafts 602, 604 arepreferably chain driven off of the right end of the forward crankshaft.The cam followers 606, 608 are preferably made of forged carbon steel.The cam shafts 602, 604 are specifically designed in conjunction withthe porting configuration to provide an abundance of air to thecylinder. The cam shafts 602, 604 are typically made of billet or forgedsteel. The cams 602, 604 are desirably equipped with variable valvetiming controlled by the Engine Control Unit (ECU).

Use of the large diameter cylinder and relatively short stroke(oversquare configuration), in combination with the improved portingsystem, produces multiple benefits. These benefits include high poweroutput and long engine life with relatively low mean piston speed,associated higher reliability, and reduced manufacturing costs.

Moment-Cancelling 4 Stroke Engine Porting

The MC4S engine porting has features that include intake and exhaustvalve configurations and intake porting that preferably result in asignificant engine performance enhancement as the result of improveddelivery of air into the combustion chamber. Experiments have shown thatthe careful matching of air movement shown herein along with fueldistribution can have a dramatic effect on engine performance.

In some embodiments, the double tapered intake port preferably has acurved transition on the longer side of port to help offset the airvolume of valve stem, as shown in FIG. 6. In addition, on the short sideof the port, the radius of the port transition preferably expandsslightly to meet the valve seat. These “pigeon toe ports” (convergingports) enhance the burning of extra lean mixtures and significantlyimprove combustion.

The valves 620, 622 may be made of various materials including varioustemperature resistant steels as well as Titanium, and ceramics. In thehead, the valve seat can be made of various materials includingcopper-beryllium, bronze, steel, or ceramics.

FIG. 7 shows a cross-section of the intake valve in close proximity tothe head. The valve diameter 702 is the diameter of the radially outermost edge of the surface defining the valve seat along a cross-sectionperpendicular to the axis of movement of the valve. The valve seat width704 is the length of the surface extending from the radially outermostedge of the valve seat surface to the radially innermost edge of thevalve seat surface.

Experiments and analyses have shown that small changes in intake andexhaust valve angles can have significant effects on engine performance.Over 200 variations of valve configurations have shown that thepreferred embodiment as illustrated can result in a 15% increase in thevolume of air (cubic feet/minute) delivered at high velocities (0.5-0.95Mach). In comparison, normally-aspirated engines have intake velocitiesless than 0.4 Mach and the associated less volume of air.

Another significant design feature of the illustrated engine is therelationship of intake valve area (sq. in.) to bore area (sq.in.). Thisrelationship can affect the “breathing” of the engine by providinggreater delivery of air into the chamber with the physical constraintsof the bore size. For example, for the dual intake valve and dualexhaust valves for the flat head piston engine shown, the range of thecombined area of the two intake valves is preferably 28-38% of the borefor pistons of 1.5 inch to 7 inch range and engine strokes of 1.5-3.5inches.

A similar relationship of exhaust valve area (sq. in.) to bore diameterhas a preferred range of 14-20% and for bores of 1.5-7.0 inches andengine strokes of 1.5-5.

Another significant design feature is the relationship of the port areato the valve area. For the MC4S engine, the intake port area to valvearea has a range of 42-65% of the valve area with the preferredembodiment of 53.4%.

Another significant design feature of the illustrated engine 100 is theangle of the intake and exit port angle. The intake port angle ispreferably about 7.9 degrees left of vertical and the exhaust port angleis preferably about 8.4 degrees right of vertical for an inclusive angleof about 16.6 degrees.

The MC4S engine 100 also expands the operating envelop of the Ottocycle. Because of the increased air mass delivered into the piston, theoverall engine work capacity is increased. See the Otto cycleillustration shown below in FIG. 8.

Another example of the benefits of the described MC4S porting system ismanifest in increases in power from the engine. FIG. 8 illustrates anOtto cycle for an engine with and without the improved porting disclosedherein. Specifically, using the MC4S engine without the MC4S portingsystem, the engine generally produces a maximum of about 141 hp.However, with the MC4S porting system the same engine produces about 262hp, or an 85% increase in power, as illustrated by the shaded area inFIG. 8. This dramatic difference is the result of delivering the airdeeply and efficiently into the bore and producing an efficientcombustion process.

In addition, the intake system may be equipped with a throttle valve atits entrance. Engine Management electronics may optionally control thethrottle valve into multiple positions. With the Engine Managementcontrolling the variable cam timing and “throttle-by-wire” via thethrottle valve, the engine may operate in a “high mileage” mode that mayprovide good fuel mileage and adequate power and a “Sporty mode” thatprovides greater engine power.

It can be seen by someone skilled in the art that the above combinationof features (port shape and angles, valve shape-seat shape, valve areato piston area) are inter-related to provide optimum delivery of air tothe engine with the associated benefits of better combustion efficiency,greater power, and higher engine torque, which in combination withcontrol over squish, compression ratio, piston stroke, and piston sizepreferably results in an engine optimized for multiple parameters. Forexample, the lower compression ratio reduces the potential fordetonation. In another example, a more efficient flow through the portsresults in less lift required of the valves, which results in lessspring load required for the valves, which results in less wear on thecamshafts. In yet another example, the combination of lower compressionratio and better delivery of air flow allows the use of conventionalfuels that burn with less NOx and COx emissions.

When the above described porting system is combined with an EngineControl Unit (ECU), the result is significantly lower NO and CO gasesbecause of the additional availability to air for combustion.

Crankshaft Features

The design of the crankshaft for the MC4S engine has several uniqueaspects. FIG. 9 shows an isometric view of one of the crankshafts 900 ofthe MC4S engine.

The two crankshafts for the two pistons are preferably mountedperpendicular to the longitudinal axis of the vehicle, such as on amotorcycle, and are designed to rotate in opposite directions. When theMC4S engine is operating, the rotational moments created by thecrankshafts preferably cancel each other (Moment-Cancelling), whichprevent a common problem with crankshafts parallel to the axis of thevehicle, that is, greater difficulty and effort in turning in onedirection than the other due to the gyroscopic effect.

In the four-stroke MC4S engine illustrated herein, the two crankshaftsare preferably synchronized by meshing a gear on each crankshaft,thereby determining the timing of the pistons to each other.

Another significant benefit of the two crankshafts rotating in oppositedirection in the MC4S engine is the reduction in transverse motionimparted to the vehicle as a result of cancelling the horizontalimbalance. During any 4-stroke cycle, both vertical and horizontalforces are placed on the bore by the rotation of the connecting rods andtransmitted to the crankshaft. In many conventional engines, thisimbalance is manifested as a forward and backward rocking motion in amotorcycle with an engine without a rotating balancing crankshaft.However, in the MC4S, this motion is preferably cancelled within themotor, again resulting in a low vibration engine.

Another benefit of the moment cancelling crankshafts is simplicity.Specifically, in some 4-stroke engines with a single crankshaft,rotating balance shafts are incorporated to reduce vibration, thusadding costs and complexity and not preventing the problems but onlyameliorating them. The presented MC4S engine desirably circumvents thiscomplexity.

Other important benefits of reduced engine vibration are improvedbearing life, increased simplicity through the prevention of use ofvibration dampers, and reduction in stresses in the motor and on thevehicle.

As shown in FIG. 1B, the crankshafts use gears and a chain as part of achain drive system 150 to drive the camshafts. As a result of the smoothoperation of the crankshafts, the camshafts preferably see lessvibration, desirably resulting in long operational life of the connectedcomponent.

Another important feature of the crankshaft 900 for the MC4S engine isits extremely short length for a two cylinder engine. Because thecrankshaft design for two cylinders is equivalent in length to a singlecrankshaft, the relatively short length adds to the rigidity (henceresistance to bending) of the assembly. When placed in combination withmodern ball-bearings, the result is desirably minimum bending-inducedvibration and longer bearing life.

The crankshaft 900 can be made of various materials but typically it ismade from high strength alloy steels; however, other materials may beused including Titanium alloys. In some embodiments, various coating andhardening processes may be applied to the crankshaft including nitridingsteel to enhance wear characteristics.

Bearing loads were calculated at numerous positions during therotational cycle from which the lubrication scheme was developed. Again,because of reduced vibration, bearing life is desirably improved becausethe fluid bearing is not periodically collapsed.

In addition, the smooth motion of the moment-cancelling crankshafts ofthe MC4S engine desirably helps prevent the superposition of vibratoryaccelerations on the valve train, thereby again increasing operatinglife.

In some embodiments, the crankshafts feature heavy duty splines andgears that facilitate driving other engine elements efficiently. Theright end of the forward crankshaft 102 (FIG. 1B) is used to drive theoil pump and via chain drive to the cam shafts. The left side rearcrankshaft 104 drives a gear, then through an idler gear to thetransmission and ultimately to the power train and the left forwardcrankshaft 102 drives the alternator.

The design and orientation of the crankshafts for the MC4S enginedesirably results in the benefits of ease in turning the vehicle andreduction in engine vibration in multiple locations with associatedgreater reliability and lower operating cost, as well as a compactengine layout.

Reliability Features of Moment-Cancelling 4 Stroke Engine

As has been discussed above, a combination of features is preferablyincorporated into the MC4S engine to increase the reliability of theengine. For example, limiting the mean piston speed through thecombination of short piston stroke and operational engine speed (rpm)preferably results in longer engine life. Incorporation of themoment-cancelling crankshafts preferably produces the benefits of lowvibration, reduced potential valve and camshaft excessive vibration andinduced wear, lower intake and exhaust valve stresses, lower valvespring loads, longer cam life, and increased life of the structuralfeatures of the vehicle.

Again, because of the crankshaft configuration, a short, nearly rigidload structure resistant to bending during combustion preferablyincreases the operational life of the crankshaft bearings.

Use of the large diameter piston with short stroke preferably results inadequate power without the complexity of additional pistons (for thesame amount of power) and thus desirably substantially reducescomplexity and the probability of problems.

Use of the large diameter pistons with short stroke and the highlyefficient porting system described, along with the use of conventionalfuels, desirably allows for a lower compression ratio for the same powerwith detonation avoidance and therefore higher reliability.

Again, the combination of the unique porting system and piston sizepreferably easily produces significant power without excessive loadingof the system and thereby increases engine life. Further, the portingsystem desirably allows greater air supply and ultimate greater power.

Because of the moment-cancelling crankshafts and the resulting smoothoperation, gear life is desirably extended.

Because of the compact layout of the engine in combination with thepower generated, the localized heated areas of the engine are desirablyeasily controlled by the liquid cooling system, again increasingreliability.

The use of coating on the bore desirably allows better heat transfer tothe cooling system as the use of oil to cool the undersides of thepistons desirably reduces heat and increases engine life.

Performance-Enhancing Modifications to the Moment-Cancelling Four StrokeEngine

Another significant advancement of the MC4S engine 100 is the ease inwhich performance parameters can be enhanced. By increasing the valveacceleration rate and rpm (and hence the mean piston speed), evengreater power is desirably available. For example, for an MC4S engine asillustrated herein without the MC4S porting system and with a meanpiston speed less than 4200 feet per minute, the power is about 189 hp.For an MC4S engine as illustrated herein having the MC4S porting systemand a mean piston speed of 4200 feet per minute, the power is about 262hp. The use of the MC4S porting system desirably increases engine powerby 38%. For the MC4S engine with the MC4S porting system and a meanpiston speed above 4200 feet per minute, the power output is desirably aremarkable 303 hp. Use of the MC4S porting system and higher pistonspeed desirably result in a power increase of over 60%. This provides aquantified example of the inter-relationship of the several designfeatures listed.

Variations of the Moment-Cancelling 4 Stroke Engine

The Moment-Cancelling 4 Stroke Engine has multiple variants that areincluded within this invention. Specifically, the MC4S Engine can be ina 2-cylinder (twin), 4-cylinder (quad), 6-cylinder, and 8-cylinderconfigurations.

Benefits

-   -   Improved Air Intake: Significantly improved air flow allows the        engine to have a more complete combustion, greater engine        efficiency, greater power, lower emissions.    -   Moment-Cancelling Crankshafts: Reduces the rotational moment of        from the crankshafts allows easier turning of the vehicle        (motorcycle) and less vibration.    -   Offset cylinder: The offset of cylinders allows the connecting        rod to run straighter during the firing stroke. The result of        this is faster acceleration with less side force on the piston        skirt.    -   Moment-Cancelling Crankshaft: reduces engine vibration and        thereby decreases wear and increases overall engine and vehicle        life    -   Improve Air Intake: Greater air flow allows wide range of        compression ratios and when compression ratios are reduced the        endurance of the engine is increased and the probability of        detonation decreased.        Unexpected Results from MC4S Engine

The MC4S engine's preferable performance criteria are the following: (1)sporty engine power, using commercially available fuels, with reduceddanger of piston detonation; (2) abundant air intake without thenecessity of turbocharger; (3) long engine endurance life withoutsacrificing sporty power and torque; and (4) good fuel economy.

One method of achieving these objectives lies in the design of the airintake and exhaust system for the engine. A large number of experimentsand simulations were conducted on the MC4S Engine for the purpose ofisolating these characteristics and combination of characteristics toimprove performance.

Several intake-exhaust system and engine parameters were used toevaluate the performance objectives. These include Brake Mean EffectivePressure (BMEP) in the cylinder. BMEP is a quantity relating to theoperation of a reciprocating engine and is a valuable measure of theengine's capacity for work and power. For example, a naturally aspirateengine has a BMEP of 125-150 lbs/in². It can be thought of as the“average” piston pressure during the stroke.

Another parameter is the air flow (CFM) into the cylinder, measured incubic feet per minute. This parameter provides an indication of theamount of air available into the cylinder for combustion. Because thisis a dynamic process of the lifting of the valve, the air flow can berelated to the amount of lift displacement of the valve.

Another parameter used in characterizing engines is its compressionratio (CR). The CR is the ratio of the volume of the combustion chamberfrom its largest capacity to its smallest capacity, that is when thevolume of the cylinder when the piston is at its lowest position (bottomdead center) versus the volume of the cylinder when the piston is at itshighest position (top dead center).

As a result of extensive experiments, other characteristics important tothe air intake system were discovered. Specifically, the intake shortside radius was found to be of importance in the mixing of the air-fuel.Also, the intake valve backside radius was also found to be ofimportance.

The following presents some of the extensive data generated for the MC4Sengine and reviews several unexpected results that demonstrate that thedesign objectives achieved were significantly greater than anticipatedwith existing knowledge. Parameter ranges that produce theabove-mentioned unexpected results are discussed.

Effects and Significance of Inlet Port Taper on Pressure (BMEP) in theCylinders of MC4S Engine

For the MC4S engine's intake system, several design variations werecreated that examined the amount of flow into the cylinder. FIG. 10shows three of these intake port variations—STRAIGHT intake port,IMPROVED TAPERED port, and OPTIMIZED tapered—for various amounts ofvalve lift, allowing a comparison of the performance of each portconfiguration.

FIG. 10 reveals several unexpected results. First, the area under thesecurves is an indicator of the amount of useful air for combustion.Therefore, both the IMPROVED TAPER port and the OPTIMIZED TAPER portprovide a greater amount of air available for combustion and hencegreater work per stoke of the piston, with the OPTIMIZED TAPER portproviding the greatest amount of air and hence greater work per stoke ofthe three configurations. The significantly greater area under the flowversus valve lift (air volume) line for the OPTIMIZED TAPERconfiguration is unexpected. The OPTIMIZED TAPER configuration providesa consistently greater volume of air than the baseline STRAIGHT TAPERconfiguration or the IMPROVED TAPER configuration or any of the hundredsof other configurations evaluated.

To illustrate the physical differences in the porting system thatproduced these unexpected results, FIGS. 11A, 11B, and 11C are included.In FIG. 11A, the dimensions of an existing intake system are shown for a5 inch diameter cylinder configuration. This configuration produced theSTRAIGHT TAPER Port Flow versus Valve lift data shown in FIG. 10.Similarly, FIG. 11B shows the physical dimensions of the IMPROVED TAPERconfiguration that produced the IMPROVED TAPER data shown in FIG. 10 fora 5 inch cylinder bore. FIG. 11C shows the physical dimensions of theOPTIMIZED TAPER configuration that produced the OPTIMIZED TAPER datashown in FIG. 10, again for a 5 inch diameter cylinder. It is clear tosomeone expert in the art that FIG. 11C is one embodiment of thisinvention and that for engines with greater or lesser cylinderdisplacement, the actual dimensions would change proportionately;however, important relationships between features and performance areaffected by the range of the cylinder bore diameter.

At first review, the configurations of FIGS. 11A, 11B, and 11C appearsimilar, but detailed examination provides insights into the beneficialresults from the differences in the design. First, it must be emphasizedthat the several relationships of the various design features areinterconnected in their effects and hence it is the combination offeatures that allows the unexpected results measured.

To further illustrate the features of the invention, several importantrelationships within the design are discussed beginning with the IntakePorting of the OPTIMIZED TAPER when compared to the STRAIGHT TAPER orIMPROVED TAPER configurations. The several significant features of theseinventions are itemized with letters (A-N). (Here again, it isemphasized that two intake ports and two exhaust ports are desirablyprovided per cylinder).

Examination of FIGS. 11C and 11D in comparison to FIGS. 11A and 11Billustrates these features of this embodiment and the ranges ofapplicability of the various parameters. One critical parameter for theintake ports are the inside radii (Parameter A, B). These “inside radii”are specifically shaped to allow the flow boundary layer to effectivelyfollow the contour of the shape of the port and thereby deliver aireffectively. It is observed that when flow does not follow the insidecontour the result is increased pressure in the conduit and resultingreduced flow volume into the cylinder. These relationships areapplicable for bore cylinder diameters of 1.5 inch to 7 inch. Further,the bore diameter is directly related to the intake valve diameter whichis directly related to the exhaust valve diameter and these parametersaffect the other geometric relationships of this intake system.

In some embodiments, including the illustrated embodiment, the intakeand exhaust valve shapes at the entrance and exit to the cylinder havetwo important tapered angles—the valve seat angle and the valve undercutangle. When the valve is viewed in cross-section which contains the lineof movement of the valve stem (usually, the axis of the valve stem), asin FIG. 11D, the intake valve seat angle (F) is the angle between thesurface most distal from the valve stem at which the intake valve seatsor meets the cylinder head port (the “intake valve seating surface”) anda plane perpendicular to the axis of movement Z of the valve. Similarly,when the valve is viewed in cross-section, the intake valve undercutangle (E) is the angle between the surface of the valve adjacent to theintake valve seating surface and positioned radially inward therefrom(the “intake valve undercut surface”) and a plane perpendicular to theaxis of movement Z of the valve. To the extent that there is no planaror flat surface that defines the intake valve seating surface, F is theaverage intake valve seat angle of the points along intake valve seatingsurface. Similarly, to the extent that there is no planar or flatsurface that defines the intake valve undercut surface, E is averageintake valve undercut angle for an undercut surface length of 0.10inches of the intake valve directly adjacent to the intake valve seatingsurface and positioned radially inward therefrom. The intake valve seatangle and the intake valve undercut angle dramatically affect air flowand hence combustion, into the combustion chamber and cylinder. Separateports are desirably provided for each intake and exhaust valve. Shownare the valve seat angle and the valve undercut angle and located on thehead are the upper relief and the seat angle. For the intake valve, thevalve seat angle (F) has a range of about 40-52 degrees with a preferredembodiment of about 50 degrees or between 48 and 52 degrees and thevalve undercut angle (E) range is about 30-42 degrees with the preferredembodiment of about 40 degrees or between 38 and 42 degrees. On the headare located the seat angle with a range of about 40-52 degrees with apreferred embodiment of about 50 or between 48 and 52 degrees. For theexhaust valve, the valve seat angle R is preferably between about 40-52degrees with a preferred embodiment of about 45 degrees and the valveundercut angle S is preferably between 30-48 degrees with a preferredembodiment of about 35 degrees. Also important to overall air flowthrough the head is the shape of the intake port angle Q, which isdesirably about 50 degrees as measured from a plane perpendicular to theaxis defined by the cylinder or between 45 and 65 degrees and in theillustrated embodiment is between approximately 48 and 52 degrees.

The ranges for several characteristic parameters defined in FIGS. 11Cand 11D are preferably within the following ranges.

1.5 inches<P<7 inches (Cylinder Bore Diameter range (inches))

0.55 inches<M<2.56 inches (intake valve diameter range (inches))

Similarly and equally important for the overall performance of theintake system are the exhaust ports. The intake port configuration andthe exhaust port configuration are inter-related because despiteabundant air into the cylinder the failure to exhaust the combustedgases results in lower overall performance.

0.44 inches<N<2.06 inches (exhaust valve diameter range (inches))

0.4 inches<A<1.5 inches (first intake port inside radius range (inches))

Experiments have shown that the first intake port inside radiustransitioning to the second inside port radius is critical to obtaininga flow that does not separate when entering the port.

0.13 inches<B<0.7 inches (second intake port inside radius range(inches))

0.4 inches<G<1.85 inches (minimum intake port diameter range (inches))

0.64 inches<H<3.05 inches (maximum intake port diameter range (inches))

Another important parameter is the taper of the intake port. The use ofa taper produces a “nozzle-like” effect and accelerates the flow (viasuction) into the cylinder, as seen in FIGS. 11C and 11D.

0.45 inches<C<2.1 inches (intake bowl radius range (inches))

The parameter (C), the outside radius of the intake, establishes a“bowl” that allows greater volume in the port just prior to entrance tothe cylinder, thereby producing a velocity gradient from its surface tothe curving centerline of the port which interacts with the velocitygradient from the inside radii and interacting, especially at greatervalve lift levels, that increases flow.

0.4 inches<L<1.93 inches (exhaust port diameter range (inches))

In addition, the exhaust ports can “choke” flow if not in theappropriate shape and size hence the appropriate ranges for thisparameter is specified.

0.12 inches<I<0.56 inches (exhaust port first inside radius (inches))

0.2 inches<J<0.98 inches (exhaust port second inside radius (inches))

0.63 inches<K<3.22 inches (exhaust port outside radius (inches))

Again, a subtle difference between the OPTIMIZED TAPER, the STRAIGHTTAPER and the IMPROVED TAPER are the angles E and F defining the intakevalve. Experiments have shown that reducing the angles of the valve tendto reduce friction losses and again improve flow. These are indicated bythe following ranges.

45 deg<F<53 degrees; but preferably F=50 degrees in the preferredembodiment

35 deg<E<43 degrees; but preferably E=40 degrees in the preferredembodiment

Another important parameter is the relationship of the intake valve(s)diameter (M) to the exhaust valve diameter (N). This relationshipreflects the preference of the intake valve and exhaust valve projectedarea of the cylinder to be less than the diameter of the cylinder andallow space between the four valves in each cylinder. This is shown inthe below relationship.

1.5<2M+2N<7

45 degree<Q<55 degree Intake Port Angle

30 degree<S<40 degree Exhaust Valve undercut angle

40 degree<R<50 degree Exhaust Valve seat angle

The Intake Port Angle (Q) is important as it facilitates flow into theintake port and is convenient for engine layout.

Experiments have shown that the exhaust valve undercut angle (S) andexhaust valve seat angle (R) combine to facilitate flow out of thecombustion cylinder bore and thereby prevents a “choking” of the flowthat would inhibit the overall engine performance. As illustrated inFIGS. 11C and 11D, when the valve is viewed in cross-section, theexhaust valve seat angle (R) is the angle between the surface mostdistal from the valve stem at which the exhaust valve seats or meets thecylinder head port (the “exhaust valve seating surface”) and a planeperpendicular to the axis of movement Z′ of the exhaust valve.Similarly, when the valve is viewed in cross-section, the intake valveundercut angle (S) is the angle between the surface of the valveadjacent to the exhaust valve seating surface and positioned radiallyinward therefrom (the “exhaust valve undercut surface”) and a planeperpendicular to the axis of movement Z′ of the exhaust valve. To theextent that there is no planar or flat surface that defines the exhaustvalve seating surface, R is the average exhaust valve seat angle of thepoints along intake valve seating surface. Similarly, to the extent thatthere is no planar or flat surface that defines the exhaust valveundercut surface, S is average intake valve undercut angle for anundercut surface length of 0.10 inches of the intake valve directlyadjacent to the intake valve seating surface and positioned radiallyinward therefrom.

Note that the intake port radii A and B and the intake bowl radius Cprovide a substantial benefit by helping to pull air in to the middle ofthe combustion chamber within the cylinder to provide optimal fuel/airmixing and improved combustion. Additionally, the exhaust port radii I,J, and K also provide an important benefit in facilitating flow out ofthe cylinder and preventing a “choking” of the exhaust flow that wouldinhibit overall engine performance.

Additionally, the length O of the tapered intake port to the amount oftaper provides a substantial benefit. As the intake air flows throughthe tapered intake port, the flow velocity increases as the intake portnarrows. In combination with the intake port radii A and B and theintake bowl radius C, the length O of the tapered intake port assistswith air/fuel mixing and combustion within the combustion chamber.

Again, it should be emphasized that the combination of severalparameters achieves the recited unexpected results. It is clear tosomeone skilled in the art that using one or more of these parameterwill improve results, but the combination of these parameters discussedabove produces the recited unexpected results.

The availability of greater power also results in greater heat in thepiston/cylinder during combustion. The greater heat influx of air shouldbe offset by adequate cooling methods, and hence air cooling for theMC4S engine for a motor cycle will likely be insufficient and watercooling is preferred.

It is also important to observe that greater air flow for a specifiedamount of valve lift allows the option of shorter valve lift. Shortervalve lift results in less time and less impact on the valve resultingin greater engine endurance.

It should also be noted that the MC4S engine utilizes dual separateintake ports in order to provide the benefits of greater power. However,dual intake ports require a large amount of space. In order toaccommodate this space constraint, use of an over square large boreshort stroke engine construction is preferred. The characteristicparameters of the MC4S over square engine are discussed above.

Further, the use of dual intake ports allows the trajectory of the airflow to meet at a desired location in the cylinder producing betterair-fuel mixing. The improved air-fuel mixing allows the use of lowerquality fuels, such as commercial fuels found in gas stations, animportant design objective.

The intake porting system also produces greater power because of thesize of the ports. Due to the size of the intake ports, the preferredembodiment occupies greater space than conventional porting systems andhence the pistons are best placed in line of the axis of the vehicle. Inthis configuration, the pistons will fire in a highly uniform and smoothmanner (as compared to a V-twin, for example, which are notorious forhigh levels of vibration). To further enhance the uniform and smoothbehavior of the engine, counter-rotating crankshafts are used ratherthan a single crank. Therefore, achievement of greater power with thedisclosed porting system directly leads to the preferred use ofcounter-rotating crankshaft as to not lose the benefits of the portingsystem.

Effects and Significance of Change in Compression Ratio on Brake MeanEffective Pressure on MC4S Engine

Various compression ratios were investigated for the MC4S engine viasimulations. In separate efforts, this simulation method has been shownto be within 1% of predicted values, and therefore is usually indicativeof anticipated physical results. FIG. 12 shows these investigations forthe OPTIMIZED TAPER porting system shown above.

FIG. 12 examines the peak BMEP for the MC4S engine with the OPTIMIZEDTAPER porting system for a range of Compression Ratios from 9.0 to 10.5.As observed in FIG. 12, the peak BMEP occurs at approximately 8000 rpm.In FIG. 13, the peak BMEP at a fixed RPM is plotted for variouscompression ratios. Importantly, it should be noted that the peak BMEPfor the MC4S system is more than 100% greater than most normallyaspirated engines. This unexpected result points to a very powerfulengine resulting from the improved air supply.

Examination of FIG. 13 further reveals an unanticipated result of thedisclosed engine design. In most naturally aspirated intake systems, theBMEP is significantly increased with increasing compression ratio.However, with the MC4S engine intake system as discussed above, theeffect of increasing compression ratio levels off. This leveling offindicates that over the range of practical compression ratios,significant increase in CR does NOT produce significant increase thealready significantly high BMEP. As a result, the engine can operate ata lower CR and still produce significant power. It is well known thatlower compression ratios result in lower loads on pistons, piston rods,and bearings. As illustrated in the above figures, the MC4S engineproduces high power and has simultaneously long endurance at a lowercompression ratio than other engines with naturally aspirated intakesystems.

Additionally, higher CR increases the proclivity for detonation. TheMC4S engine as disclosed preferably effectively reduces the proclivityfor detonation without the significant loss of power, as it is able toproduce high power at a lower compression ratio. Specifically, the lossof power with lower compression ratio is typically greater than 4% formost other naturally aspirated engines while the loss of power in theMC4S engine is less than 2%, i.e., 50% less power loss because of theporting system of the MC4S.

Although not empirically verified at this time, the unexpected advantageof the MC4S engine is that greater “breathing” of the engine is ofgreater importance than compression ratio, which is the opposite fromconventional systems.

Effects and Significance of Intake/Exhaust Flow on Power

Simulations were also run to determine the effects of variations in theexhaust port size compared with the fixed intake port configurationdiscussed above for maximizing engine horsepower.

FIG. 14 shows the variation of Intake/Exhaust Flow rates at variousvalve lift positions for three porting system configurations. Case 3illustrates data from the STRAIGHT TAPER configuration shown in FIG. 11Awhich is an example of an overly restrictive exhaust. Case 2 illustratesdata from the IMPROVED TAPER port configuration and is an intermediateexample of exhaust. Case 1 illustrates data from the OPTIMIZED TAPERporting system and is an example of fully developed exhaust flow for thespecified intake.

As illustrated in FIG. 14, Cases 1 and 2 (the OPTIMIZED TAPER portingsystem and the IMPROVED TAPER porting system) produce higherintake/exhaust flow ratios at a given valve lift position than Case 3(the STRAIGHT TAPER porting system). This is indicative of the increased“breathability” of the MC4S engine.

Examination of FIG. 15 shows the effect of the range of intake/exhaustflow rates on horsepower. The range of intake/exhaust flow is defined asthe maximum to minimum flow rates during the lifting of the both theintake and exhaust valve 0.5 inches. It can been seen from FIG. 15 thatCase 1 and Case 2 (the OPTIMIZED TAPER porting system and the IMPROVEDTAPER porting system, respectively) produce significantly greater powerthan Case 3 (the STRAIGHT TAPER porting system).

FIG. 15 illustrates several unexpected results. First, Case 1 and Case 2(the OPTIMIZED TAPER porting system and the IMPROVED TAPER portingsystem, respectively) produce very similar peak horsepower. The expectedresult would be that each range of percent intake to exhaust flow wouldbe approximately evenly spaced.

This leads to the insight that the MC4S engine preferred embodiment forthe intake/exhaust flow should preferably be in the range 86-98% flow,with the range of 78-88% as another but less preferred range, and flowsless than 78% are not deemed adequate for this engine because of reducedhorsepower.

Even though the features illustrated above may be described as importantor even critical, it is not suggested that significant benefits cannotbe achieved without the specific feature being discussed.

What is claimed is:
 1. An internal combustion engine comprising a firstcylinder having a first piston and a second cylinder having a secondpiston, a first crankshaft operably connected to the first piston and asecond crankshaft operably connected to the second piston, a cylinderhead comprising at least one intake port and at least one exhaust portper cylinder, said at least one intake port connected to the firstcylinder such that fluid can pass through the at least one intake portinto the first cylinder and said at least one exhaust port connected tothe first cylinder such that fluid can pass from the first cylinderthrough the at least one exhaust port, a movable intake valve positionedat least partially within the at least one intake port configured tocontrol the flow of fluid through the intake ports, a movable exhaustvalve positioned at least partially within the at least one exhaust portconfigured to control the flow of fluid through the at least one exhaustport, the at least one intake port having a minimum intake portdiameter, a first inside radius positioned toward an intake port valveseat from the minimum intake port diameter, said first inside radiustransitioning to a second inside radius positioned toward the intakeport valve seat from the first radius so that the intake port expands tomeet the intake port valve seat, the first inside radius being greaterthan 0.4 inches and less than 1.5 inches, the second inside radius beinggreater than 0.13 inches and less than 0.7 inches, the at least oneintake port having a non-symmetric variable shape along at least aportion of a length of the at least one intake port, said movable intakevalve defining an intake valve seat angle measured between the surfaceof the movable intake valve most distal from an intake valve stem of themovable intake valve and a plane perpendicular to the axis of movementof the movable intake valve, said intake valve seat angle being betweenabout 40-52 degrees, said movable intake valve defining an intake valveundercut angle measured between the surface of the movable intake valveadjacent to an intake valve seating surface defined b the intake valveseat angle and positioned radially inward therefrom and a planeperpendicular to the axis of movement of the movable intake valve, saidintake valve undercut angle being between about 30-42 degrees, saidmovable exhaust valve defining an exhaust valve seat angle measuredbetween the surface of the movable exhaust valve most distal from anexhaust valve stem of the moveable exhaust valve and a planeperpendicular to the axis of movement of the movable exhaust valve, saidexhaust valve seat angle between about 40-52 degrees, said movableexhaust valve defining_an exhaust valve undercut angle measured betweenthe surface of the movable exhaust valve adjacent to an exhaust valveseating surface defined by the exhaust valve seat angle and positionedradially inward therefrom and a plane perpendicular to the axis ofmovement of the movable exhaust valve, said exhaust valve undercut anglebeing between about 30-48 degrees, and an intake port angle of the atleast one intake port is between about 45 and 65 degrees, wherein thefirst crankshaft rotates in a first direction and the second crankshaftrotates in a second direction such that the second direction is anopposite direction from the first direction.
 2. The engine of claim 1,wherein a bore of each of the first and second cylinders is greater than3.0 inches.
 3. The engine of claim 1, wherein a compression ratio of theengine is between 9.1 and 13.5 and an oversquare ratio of the engine isgreater than 1.0.
 4. The engine of claim 1, wherein a squish area ofeach piston is between 24%-35% of an area of the piston.
 5. An internalcombustion engine comprising a first cylinder having a first piston anda second cylinder having a second piston, a first crankshaft operablyconnected to the first piston and a second crankshaft operably connectedto the second piston, a cylinder head comprising at least one intakeport and at least one exhaust port per cylinder, said at least oneintake port connected to the first cylinder such that fluid can passthrough the at least one intake port into the first cylinder and the atleast one exhaust port connected to the first cylinder such that fluidcan pass from the first cylinder through the at least one exhaust port,a movable intake valve positioned at least partially within the at leastone intake port configured to control the flow of fluid through the atleast one intake port, a movable exhaust valve positioned at leastpartially within the at least one exhaust port configured to control theflow of fluid through the at least one exhaust port, the at least oneintake port having a minimum intake port diameter and a tapered portionupstream of said minimum intake port diameter, a first inside radiuspositioned toward an intake port valve seating surface from the minimumintake port diameter, said first inside radius transitioning to a secondinside radius positioned toward the intake valve port seating surfacefrom the first radius so that the intake port expands to meet the intakevalve port seat, the first inside radius being greater than 0.4 inchesand less than 1.5 inches, the second inside radius being greater than0.13 inches and less than 0.7 inches, the at least one intake port beingnonsymmetrical, said movable intake valve defining an intake valve seatangle measured between the surface of the movable intake valve mostdistal from an intake valve stem of the movable intake valve and a planeperpendicular to the axis of movement of the movable intake valve, saidat least one intake valve seat angle being between about 48-52 degrees,said movable intake valve defining an intake valve undercut anglemeasured between the surface of the movable intake valve adjacent to anintake valve seating surface defined by the intake valve seat angle andpositioned radially inward therefrom and a plane perpendicular to theaxis of movement of the movable intake valve, said intake valve undercutangle being between about 38-42 degrees, and an intake port angle of theat least one intake port is between about 45 and 65 degrees, wherein thefirst crankshaft rotates in a first direction and the second crankshaftrotates in a second direction such that the second direction is anopposite direction from the first direction.
 6. The engine of claim 5,wherein a bore of each of the first and second cylinders is greater than3.0 inches.
 7. The engine of claim 5, wherein a compression ratio of theengine is between 9.1 and 13.5 and an oversquare ratio of the engine isgreater than 1.0.
 8. The engine of claim 5, wherein a squish area ofeach of the first and second pistons is between 24%-35% of an area ofthe piston.
 9. The engine of claim 5, wherein the first crankshaftrotates in a first direction and the second crankshaft rotates in asecond direction that is opposite the first direction.
 10. The engine ofclaim 5, wherein at least a majority of a cross-section of a valveseating surface is straight such that at least a majority of an overallshape of the valve seating surface is cone-shaped.
 11. The engine ofclaim 5, wherein at least a majority of a cross-section of a valveundercut surface is straight such that at least a majority of an overallshape of the valve undercut surface is cone-shaped.